1. Field of the Invention
The present invention relates to polyimide membranes, and more particularly, relates to electroactive, high strength polyimide membranes and their forming method.
2. Description of Related Art
Electroactive polymers are polymers reveal electric conductivity and have been classified as a new class of materials. In past decades, research works of electroactive polymers have been extensively made due to its potential commercial applications in electronic, optical, and biological fields.
Polyimide has been widely applied in industry due to its good thermal stability, mechanical and adhesion properties, wear resistance, chemical resistance, and low dielectric constant. Polyimide may be synthesized via condensation or addition method. The condensation method is further divided into a one-step method and two-step method.
In 1988 Wang et al. [Wang Z Y, Yang C, Gao J P, Lin J, Meng X S, Wei Y, Li S. Macromolecules 1998; 31(8): 2702-4] discovered that amine-capped aniline trimer (ACAT) reacting with anhydride will generate low yield and low molecular weight of electroactive polyimide, because the amine-capped aniline trimer reduce the probability to meet anhydride. Accordingly, Wang et al. proposed a forming method of polyimide, which is to reduce ACAT by PtO2/H2 firstly, and then the reduced ACAT is reacted with anhydride so that high yield electroactive polyimide can be obtained. However, the Wang et al. method is complicated.
In addition, polyimide synthesized by the prior art has insufficient degree of polymerization and thus is difficult to be produced in the form of a membrane. Even though a polyimide membrane could be made, its low Young's Modulus (less than 2 GPa) and poor workability limit the applications.
Accordingly, it would be advantageous to provide high strength and high molecular weight of polyimide membranes and their forming methods for improving the workability and broadening the applications.